Oil Pump

[MartyNZ]

After having the oil module and cooler off my bike, I thought I should prime the parts with fresh oil. I was surprised to find that oil pumped through the oil pump at quite low pressure. Does this mean the pump is worn? I thought a positive displacement gear pump wouldn't allow oil past unless it was turning.

Picture below shows filling and purging the empty oil cooler.

Picture below shows pumping oil into the oil pump intake. Oil flows with pressure above 68kPa (10psi) and eventually drips down from above.

[docc]

Moved @MartyNZ's post to its own topic owing to its importance.

 

[Weegie]

Interesting I've never heard anybody try that experiment

Unless something catastrophic had happened to the engine at some point or the mileage was ludicrously high, I'd doubt it, however I've no real idea of what would constitute a worn pump. There has to be gear clerances, but what these are I've no idea.

Real test is engine oil pressure, what is start up pressure on cold oil and what's the normal running pressure?

My Sport, the nearest I have to a V11, will hit 70psi or so on a cold engine running 15/50 grade oil at 20C ambient, I notice you're using a 5/50 Penrite it may be a little lower, but probably not as much as you'd imagine, if at all.

Normal running at 90-100C I get 60psi all day long.

If you're getting something similar then I wouldn't have any concerns

It'll be interesting to hear other opinions

[Lucky Phil]

11 hours ago, MartyNZ said:

After having the oil module and cooler off my bike, I thought I should prime the parts with fresh oil. I was surprised to find that oil pumped through the oil pump at quite low pressure. Does this mean the pump is worn? I thought a positive displacement gear pump wouldn't allow oil past unless it was turning.

There's quite a bit of loss through a gear pump. There's the tooth tip to housing clearance and the gear end clearance to the crankcases. With the small volume your hand pump is delivering you'll notice these accumulated losses.

I understand your reasoning here with priming but it's a bit of an overkill. The oil cooler really doesn't come into it as it's not in the oil delivery system until the thermostat opens anyway although there will be some leakage and that will gradually fill it until the thermostat opens. On a new engine it's worth running the pump off a hand drill when the front cover is off but otherwise not really necessary.

Ciao

[Pressureangle]

Ever see a moment pass by when you have specific information, but wonder if it should see the light of day? This is one of those moments.

There was a discussion about oil pumps back in the '90s when I was racing 883 Sportsters. They have a georotor oil pump. The question at hand, an academic one, is why H-D went to georotor after decades with a gear pump in that place. One guy who happened around during the discussion was an automotive engine builder of some renoun; he said he'd been told that gear pumps with high pressures had the problem of pressure spikes when they were too tight, and that bleeding mitigated those spikes. No consequence of those spikes was put forth. The trade-off was that idle oil pressure was reduced. 
Upon building a small-block Chevrolet for my pickup truck last summer, I saw offered a spiral-cut gear pump for high-pressure/performance applications, with the claim to reduce pressure spikes. The claim was that these pressure spikes increased hydraulic lifter pump-up particularly in 'stock' or 'limited modification' engines. 
Meh. Who knows? H-D went to the Georotor pump at the same time they started using hydraulic lifters in the Sportsters. 
I do know that in most American engines, distributor/oil pump drive gears are a point of failure, and it's critical to choose compatible components. Maybe there's something there on the durability scale.

My daily navel-gazing. 

[Lucky Phil]

15 minutes ago, Pressureangle said:

Ever see a moment pass by when you have specific information, but wonder if it should see the light of day? This is one of those moments.

There was a discussion about oil pumps back in the '90s when I was racing 883 Sportsters. They have a georotor oil pump. The question at hand, an academic one, is why H-D went to georotor after decades with a gear pump in that place. One guy who happened around during the discussion was an automotive engine builder of some renoun; he said he'd been told that gear pumps with high pressures had the problem of pressure spikes when they were too tight, and that bleeding mitigated those spikes. No consequence of those spikes was put forth. The trade-off was that idle oil pressure was reduced. 
Upon building a small-block Chevrolet for my pickup truck last summer, I saw offered a spiral-cut gear pump for high-pressure/performance applications, with the claim to reduce pressure spikes. The claim was that these pressure spikes increased hydraulic lifter pump-up particularly in 'stock' or 'limited modification' engines. 
Meh. Who knows? H-D went to the Georotor pump at the same time they started using hydraulic lifters in the Sportsters. 
I do know that in most American engines, distributor/oil pump drive gears are a point of failure, and it's critical to choose compatible components. Maybe there's something there on the durability scale.

My daily navel-gazing. 

I was doing some research for Joe Caruso on the latest iteration of his aftermarket oil pump and was postulating along with him on the reasoning behind using helical gears in the std pump as opposed to straight cut gears. I was looking at one of my pumps on the bench and the only advantage I could see was that as the gear tooth passed the inlet and outlet ports in the housing it did so in a gradual manner due to the angle of the tooth and not open and shut as a straight tooth would. I thought this would lead to less pressure spikes and a more constant delivery. So after about 3 hours of research I found that I was indeed correct and even found a pressure graph demonstrating the differences. Another puzzle solved and the satisfaction of realising that I had worked it out myself and the thought that maybe just maybe all the time I've devoted to thinking about "engineering" over the last 50 years or so has actually taught me stuff. A rare moment indeed. I once read as a teenager all about the pros and cons of Georotor pumps but have forgotten what they were, lol. Time to revisit.

Ciao

[Weegie]

12 hours ago, Pressureangle said:

I do know that in most American engines, distributor/oil pump drive gears are a point of failure, and it's critical to choose compatible components. Maybe there's something there on the durability scale.

My daily navel-gazing. 

On that point, years back the gas turbines I ocassionaly worked on used a flow divider to distribute distillate (liquid) fuel to the individual cans on the engine. What happened was fuel was delivered from the pump and filters to the flow divider and the fuel was delivered into a common inlet. The flow divider had had 10 gear pairs which turned due to fuel pressure on the common side and delivered to the cans on the low pressure side. Like 10 guzzi oil pumps arranged back to back in series, all the gears were linked to each other so all had to turn at the same speed.

Apparently when they made these things the tolerances were so tight that they simply manufactured the gears measured them and placed them into a stock pile. At assembly gear pairs were then matched from the stock, the tolerances being so tight that they could not just build a set of gears for a divider.

[MartyNZ]

On 11/10/2021 at 6:11 AM, Weegie said:

Real test is engine oil pressure, what is start up pressure on cold oil and what's the normal running pressure?

My Sport, the nearest I have to a V11, will hit 70psi or so on a cold engine running 15/50 grade oil at 20C ambient, I notice you're using a 5/50 Penrite it may be a little lower, but probably not as much as you'd imagine, if at all.

Normal running at 90-100C I get 60psi all day long.

Using a hand pump, I could easily exceed the gauge range limit of 60psi, and, after 20 seconds got oil dribbling down from above. I don't have any concerns now about oil pressure.

On 11/10/2021 at 10:37 AM, Lucky Phil said:

...was postulating  ... on the reasoning behind using helical gears in the std pump as opposed to straight cut gears.

Thanks for the advice and comments. Helical gears explain why I could force oil past the main oil pump.

Now I should be able to use that little hand pump to test a pressure regulator.

[Weegie]

Hi @MartyNZ I'm struggling then, if the pump is reaching rated pressure on the engine, then what's the problem?

AFAIK, a postive displacement gear pump's output is only dependent on RPM and suction (sic) pressure, assuming a given fluid viscosity. The pressure/flow realtionship in the system is dicated by the leakage paths & clearances. If the pump was worn, your running pressure would drop. I don't think it's possible to maintain pressure but have lower flow (if that's what you're drving at), I'm not sure.

Sort of similar to the Voltage/Current relationship, I'm no pump expert but have done a little experimentation on my HiCam and a bit of research over the years.

[MartyNZ]

22 hours ago, Weegie said:

Hi @MartyNZ I'm struggling then, if the pump is reaching rated pressure on the engine, then what's the problem?

No problem Weegie, I was just surprised by how easy it was to pump oil through the oil pump. 

 

[Weegie]

Oh just to add @MartyNZ thanks for the experiment and for sharing the outcome

Really appreciate when people take the time to post up insights into the engine in any shape of form

John

[p6x]

Gear pumps are flow through.

I used Sundyne pumps early in the 80's. They were equipped with by-passes and regulation valves at the outlet. But after use, you had to isolate them, else you could get flow back.

 

[Pressureangle]

31 minutes ago, p6x said:

Gear pumps are flow through.

I used Sundyne pumps early in the 80's. They were equipped with by-passes and regulation valves at the outlet. But after use, you had to isolate them, else you could get flow back.

 

We all know what happens when you leave an iron H-D or old English dry sump sit a month, don't we?  ...don't we...?

[Chuck]

It keeps the mosquitos away, though..

[Lucky Phil]

10 hours ago, Pressureangle said:

We all know what happens when you leave an iron H-D or old English dry sump sit a month, don't we?  ...don't we...?

Depends whether the pump feed check valve is functioning ok.

Ciao